iOS Device SDK

Learn how to accept payments at the point of sale using the Finix iOS Device SDK.

The Finix iOS Device SDK enables your sellers to accept payments using your iOS application and a payment terminal.

When you process payments with Finix and an iOS app, there are five main components:

Your iOS point of sale application.
The backend infrastructure which supports your iOS app.
The iOS Device SDK.
Finix's API.
A pre-certified BBPOS Chipper 2X payment terminal.

Since this solution is pre-certified with major card networks, you can integrate and deploy quickly while remaining secure and without having to perform any extra network certifications.

Payment Terminal

The iOS Device SDK works with BBPOS Chipper 2X payment terminals. These lightweight pre-certified payment terminals can accept payments from all major card brands and supports multiple card entry modes (e.g., Contactless, Chip, Magstripe, NFC wallets like Google Pay/Apple Pay, etc.).

The payment terminal provides end-to-end encryption by encrypting the sensitive card data as soon as the card information is read.

iOS Device SDK Overview

Take the following steps to integrate your point of sale iOS application with the Finix iOS SDK:

Step	Platform Component	Finix Component	Description
1. Onboard Merchants	Your platform's backend.	Finix's API	Onboard merchants and set up their point-of-sale devices to accept in-person payments (also known as Card Present transactions).
2. Pair Terminals to Device Profiles	POS iOS application	Finix iOS Device SDK	Initialize the iOS Device SDK and connect (or disconnect) BBPOS payment terminals to point of sale device profiles.
3. Accept In-Person Payments	POS iOS application	Finix iOS Device SDK	Enable the POS iOS application to accept in-person payments.
4. Post Payments Experience	POS iOS application	Finix iOS Device SDK	Manage refunds, settlements, reports, and more.

The iOS Device SDK facilitates communication between your point of sale application, the payment terminal, and the Finix API.

Finix Mobile SDK Overview

Step 1: Onboard Merchants

To use the Finix Device SDK you must create a Merchant specifically for point of sale payments.

This includes creating an Identity resource and:

Provisioning the Merchant for in-person payments.
Creating the necessary Finix credentials for that Merchant.
Creating a Device resource for the POS sale device the Merchant will use.

Taking these steps ensures that every payment gets tied to that Merchant only.

Step 1a: Provision Merchant

After you've created an Identity, you can provision your seller for in-person payments. To provision a seller send a POST request to /identities/IDENTITY_ID/merchants. After provisioning the seller, you get a Merchant ID that starts with "MUxxx".

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curl https://finix.sandbox-payments-api.com/identities/IDuWtgdP9VERb4FiLeYatWy/merchants \
        -H "Content-Type: application/json" \
        -H 'Finix-Version: 2022-02-01' \
        -u "USjHFGYvecE4LBitYG8KDE2g:b698f403-d9b7-4157-82d8-162cea8c8cc3" \
        -d '
        {
            "gateway": "TRIPOS_MOBILE_V1",
            "processor": "VANTIV_V1"
        }'

URL Parameters

Parameter	Description
:IDENTITY_ID:	ID of the `Identity`.

Request Arguments

Field	Type	Description
`gateway`	string, required	Name of the gateway that processes the `Merchant's` transaction. Include TRIPOS_MOBILE_V1 to process in-person payments with Finix's Device SDK and a payment terminal .
`processor`	string, required	Name of the `Merchant's` transaction processor. Include VANTIV_V1 to process in-person payments with Finix's Device SDK and a payment terminal.
`tags`	object, optional	Key value pair for annotating custom meta data (e.g. order numbers).

Example Response

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{
    "id": "MU4SUi7ZpghWZ6bar4SjusWb",
    "created_at": "2022-10-10T06:03:32.39Z",
    "updated_at": "2022-10-10T06:03:32.39Z",
    "application": "APeUbTUjvYb1CdPXvNcwW1wP",
    "card_cvv_required": false,
    "card_expiration_date_required": true,
    "convenience_charges_enabled": false,
    "creating_transfer_from_report_enabled": false,
    "default_partial_authorization_enabled": false,
    "fee_ready_to_settle_upon": "RECONCILIATION",
    "gross_settlement_enabled": false,
    "identity": "IDuWtgdP9VERb4FiLeYatWy",
    "level_two_level_three_data_enabled": false,
    "mcc": null,
    "merchant_name": null,
    "merchant_profile": "MP8eDsxwLS2hBdHpgAHrHWMm",
    "mid": null,
    "onboarding_state": "PROVISIONING",
    "processing_enabled": false,
    "processor": "VANTIV_V1",
    "processor_details": {},
    "ready_to_settle_upon": "RECONCILIATION",
    "rent_surcharges_enabled": false,
    "settlement_enabled": false,
    "settlement_funding_identifier": "UNSET",
    "surcharges_enabled": false,
    "tags": {},
    "verification": "VI3dEyz1wfuLmLtAMnWFcKqj",
    "_links": {
        "self": {
            "href": "https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb"
        },
        "identity": {
            "href": "https://finix.sandbox-payments-api.com/identities/IDuWtgdP9VERb4FiLeYatWy"
        },
        "verifications": {
            "href": "https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb/verifications"
        },
        "merchant_profile": {
            "href": "https://finix.sandbox-payments-api.com/merchant_profiles/MP8eDsxwLS2hBdHpgAHrHWMm"
        },
        "application": {
            "href": "https://finix.sandbox-payments-api.com/applications/APeUbTUjvYb1CdPXvNcwW1wP"
        },
        "verification": {
            "href": "https://finix.sandbox-payments-api.com/verifications/VI3dEyz1wfuLmLtAMnWFcKqj"
        }
    }
}

Get the Provisioning Status

It can take up to 20 minutes to successfully provision a merchant. Fetch the onboarding_state of the Merchant to check the status of the provisioning request (or wait for a webhook notification).

Once provisioned, the onboarding_state of the Merchant updates to APPROVED.

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curl https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb \
        -H "Content-Type: application/json" \
        -H 'Finix-Version: 2022-02-01' \
        -u "USjHFGYvecE4LBitYG8KDE2g:b698f403-d9b7-4157-82d8-162cea8c8cc3"

Example Response

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{
    "id": "MU4SUi7ZpghWZ6bar4SjusWb",
    "created_at": "2022-10-10T06:03:32.39Z",
    "updated_at": "2022-10-10T06:04:01.64Z",
    "application": "APeUbTUjvYb1CdPXvNcwW1wP",
    "card_cvv_required": false,
    "card_expiration_date_required": true,
    "convenience_charges_enabled": false,
    "creating_transfer_from_report_enabled": false,
    "default_partial_authorization_enabled": false,
    "fee_ready_to_settle_upon": "RECONCILIATION",
    "gross_settlement_enabled": false,
    "identity": "IDuWtgdP9VERb4FiLeYatWy",
    "level_two_level_three_data_enabled": false,
    "mcc": null,
    "merchant_name": null,
    "merchant_profile": "MP8eDsxwLS2hBdHpgAHrHWMm",
    "mid": null,
    "onboarding_state": "PROVISIONING",
    "processing_enabled": false,
    "processor": "VANTIV_V1",
    "processor_details": {
        "acceptor_id": "5998737400656",
        "accepted_cards": "[{type=Visa}, {type=MasterCard}, {type=Discover, attributes=[{name=Acquired, value=Yes}, {name=null, value=null}]}, {type=AmericanExpress, attributes=[{name=AmexProgram, value=OptBlue}, {name=ReceiveOptBlueMarketing, value=No}, {name=null, value=null}]}]",
        "default_terminal_id": "X6600026601",
        "mid": "5998737400656",
        "account_token": "04F4C1136F0C3EF3BEC98FE0704659029118DC5CD4A2875BD8020AFB97B50F41BB7E0A01",
        "account_id": "1052250",
        "merchant_ident_string": "5998737400656",
        "id": "192549926",
        "vantiv_merchant_id": "5998737400656"
    },
    "ready_to_settle_upon": "RECONCILIATION",
    "rent_surcharges_enabled": false,
    "settlement_enabled": false,
    "settlement_funding_identifier": "UNSET",
    "surcharges_enabled": false,
    "tags": {},
    "verification": "VI3dEyz1wfuLmLtAMnWFcKqj",
    "_links": {
        "self": {
            "href": "https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb"
        },
        "identity": {
            "href": "https://finix.sandbox-payments-api.com/identities/IDuWtgdP9VERb4FiLeYatWy"
        },
        "verifications": {
            "href": "https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb/verifications"
        },
        "merchant_profile": {
            "href": "https://finix.sandbox-payments-api.com/merchant_profiles/MP8eDsxwLS2hBdHpgAHrHWMm"
        },
        "application": {
            "href": "https://finix.sandbox-payments-api.com/applications/APeUbTUjvYb1CdPXvNcwW1wP"
        },
        "verification": {
            "href": "https://finix.sandbox-payments-api.com/verifications/VI3dEyz1wfuLmLtAMnWFcKqj"
        }
    }
}

Step 1b: Create Merchant Credentials

All Finix Device SDK calls require ROLE_MERCHANT or ROLE_PARTNER credentials. Once created, you can use these credentials across multiple devices.

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curl https://finix.sandbox-payments-api.com/identities/IDuWtgdP9VERb4FiLeYatWy/users \
-H "Content-Type: application/json" \
-H 'Finix-Version: 2022-02-01' \
-u "USjHFGYvecE4LBitYG8KDE2g:b698f403-d9b7-4157-82d8-162cea8c8cc3" \
-d '{}'

HTTP Request

GET https://finix.sandbox-payments-api.com/identiities/:IDENTITY_ID:/users

URL Parameters

Parameter	Description
:IDENTITY_ID:	ID of the `Identity`.

Example Response

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{
    "id": "USxxxxxxxxxxxxxxxxxxxxxx",
    "created_at": "2022-10-10T06:05:08.11Z",
    "updated_at": "2022-10-10T06:05:08.11Z",
    "enabled": true,
    "identity": "IDxxxxxxxxxxxxxxxxxxxxxx",
    "password": "xxxxxxxxxxxxxxxxxxxxxx",
    "role": "ROLE_MERCHANT",
    "tags": {},
    "_links": {
        "self": {
            "href": "https://finix.sandbox-payments-api.com/users/USgymgj1dSkCNxYmZKd9GxQN"
        },
        "applications": {
            "href": "https://finix.sandbox-payments-api.com/applications"
        },
        "application": {
            "href": "https://finix.sandbox-payments-api.com/applications/APeUbTUjvYb1CdPXvNcwW1wP"
        }
    }
}

Step 1c: Create Device

Once you've provisioned the Merchant , you'll need to create a Device to manage how the payment terminal gets configured. A Device resource represents a payment terminal and is required for merchants to process transactions with Finix.

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curl https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb/devices \
-H "Content-Type: application/json" \
-H 'Finix-Version: 2022-02-01' \
-u "USjHFGYvecE4LBitYG8KDE2g:b698f403-d9b7-4157-82d8-162cea8c8cc3" \
-d '{
    "name": "Terminal 1",
    "model": "BBPOS",
    "description": "John Smith"
}'

HTTP Request

POST https://finix.sandbox-payments-api.com/merchants/:MERCHANT_ID:/devices

URL Parameters

Parameter	Description
:MERCHANT_ID:	ID of the `Merchant` .

Request Arguments

Field	Type	Description
`description`	string, optional	Additional information about the device (e.g. self serving terminal).
`model`	string, required	Include BBPOS or LINK_2500 to let Finix know what type of device is being used.
`name`	string, required	The display name of the `Device` used for filtering purposes.
`tags`	object, optional	Key value pair for annotating custom meta data (e.g. order numbers).

Example Response

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{
    "id": "DVdWhYkdEQPurNMX6tzy94CK",
    "created_at": "2022-10-10T06:06:08.936946Z",
    "updated_at": "2022-10-10T06:06:08.936946Z",
    "configuration_details": {
        "allow_debit": true,
        "check_for_duplicate_transactions": true,
        "prompt_amount_confirmation": true,
        "prompt_manual_entry": false,
        "prompt_signature": "ALWAYS",
        "signature_threshold_amount": 0,
        "bypass_device_on_capture": true
    },
    "description": "John Smith",
    "enabled": true,
    "idle_message": null,
    "merchant": "MU4SUi7ZpghWZ6bar4SjusWb",
    "model": "BBPOS",
    "name": "Terminal 1",
    "serial_number": null,
    "tags": {},
    "_links": {
        "self": {
            "href": "https://finix.sandbox-payments-api.com/devices/DVdWhYkdEQPurNMX6tzy94CK"
        },
        "merchant": {
            "href": "https://finix.sandbox-payments-api.com/merchants/MU4SUi7ZpghWZ6bar4SjusWb"
        },
        "transfers": {
            "href": "https://finix.sandbox-payments-api.com/transfers"
        },
        "authorizations": {
            "href": "https://finix.sandbox-payments-api.com/authorizations"
        }
    }
}

Step 2: Pair Terminals

After creating a Device, you need to install the iOS Device SDK and prepare the payment terminals and your iOS application:

Using the iOS Device SDK, connect the iOS application to a Device created under the merchant’s Finix account.
Pair the iOS application with a payment terminal.

Install the iOS Device SDK

Ask your Finix point of contact to get access to the iOS Device SDK. Installing the iOS Device SDK depends on the triPOSMobileSDK.xcframework, which is included.

iOS Compatibility

The Finix iOS Device SDK only supports iOS 12 and later.

Before installing the iOS Device SDK, make sure the triPOSMobileSDK.xcframework is included.

Make sure to add it to your project, along with embedding it in your target and linking against it.
Clone/copy FinixPOS at the same level of your project.

The XCFramework takes care of updating source code dependencies, so there's no need to update “Framework Search Paths”.

POS iOS App Requirements

Using the iOS Device SDK in an app adds specific dependencies that need to be configured:

Framework Dependencies

The following frameworks must be linked in order to run the iOS Device SDK.

ExternalAccessory.framework - a system library.
triPOSMobileSDK.xcframework - must be embedded.
FinixPOS.xcframework - must be embedded.

Info.plist

The iOS Device SDK connects to the BBPOS payment terminal using Bluetooth Low Energy (BLE). To support this, the iOS Device SDK requires the following to get added to the application’s Info.plist to access BLE:

Privacy - Bluetooth Peripheral Usage Description - aka NSBluetoothPeripheralUsageDescription
Privacy - Bluetooth Always Usage Description - aka NSBluetoothAlwaysUsageDescription

BLE allows the automatic pairing of a device to an application. Considering this, DO NOT PAIR the terminal manually using the iOS device's Bluetooth Settings.

Your app can't connect to the terminal if it's been manually paired from the iOS device's Settings. If you pair the device via the device's Bluetooth settings, you need to disconnect the terminal from the Bluetooth Settings of your iPad or iPhone.

Once the's iOS Device SDK is installed and added to your project, you can reference the framework by importing FinixPOS.

The iOS Device SDK is a singleton. It can be accessed via the shared instance.

Initializing the SDK

To process payments the iOS Device SDK must be initialized so the SDK instance is connected to a Device on the merchant’s Finix account and paired over Bluetooth to the payment terminal.

Before initializing the SDK, power “ON” the BBPOS payment terminal and place it near the iPad/iPhone. The terminal flashes a blue light when it's in the pairing mode.

Finix merchant credentials (ROLE_MERCHANT) are required for this step. We recommend storing these credentials on your backend system, so they can be retrieved after you authenticate the merchant.

The iOS Device SDK gets initialized with a FinixConfig struct which contains the SDK configuration information. It has the following constructor:

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init(environment: Finix.Environment,
            application: String,
            credentials: Finix.APICredentials,
            deviceId: String,
            deviceType: Finix.Device,
            merchantId: String,
            version: String,
            serialNumber: String? = nil)

Parameters

Parameter	Description
`environment`	Sandbox or Live
`application`	The application description.
`credentials`	Your Finix merchant credentials. They should be fetched from your backend service and then used to initialize the iOS Device SDK.
`deviceId`	The ID of the `Device` created for this merchant. Use the ID returned when creating a `Device`.
`deviceType`	The type of the payment terminal. Set to BBPOS
`merchantId`	The ID of the `Merchant` .
`version`	The application version.
`serialNumber`	The serial number of the payment terminal (Optional). If included, the SDK will only attempt to connect to the terminal with the matching serial number. If left blank, the SDK connects to any available paired device.

The syncSDK() call is asynchronous. Don't make any API calls until the operation completes and the handler gets called.

After the sync call completes, the payment terminal will begin to scan for devices. The terminal searches for a payment terminal to pair with for one minute. After pairing with a device, the terminal will be ready to process card transactions.

To verify a successful pairing the delegate will receive deviceDidConnect(_:model:serialNumber:).

You can also check FinixClient.shared.isReaderConnected to verify the connection state.

Here is an example initialization:

import FinixPOS

Note: To get credentials and deviceId, your Finix credentials should be fetched from your backend server in order

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let credentials = Finix.APICredentials(username:TEST_USERNAME, password:TEST_PASSWORD)
let deviceId = TEST_DEVICEID

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func initializeFinixSDK() {
        let config = FinixConfig(environment: .TestCertification,
                                 credentials: credentials,
                                 application: TEST_APPLICATION,
                                 version: TEST_VERSION,
                                 merchantId:TEST_MERCHANTID,
                                 deviceType: .BBPOS,
                                 deviceId: deviceId)

Set delegates

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   let client = FinixClient.shared
   client.delegate = self
   client.interactionDelegate = self

   client.syncSDK(config:config){ (success, error) in
            guard success == true else {
                print("FinixSDK: failed to initialize with error \(error!)")
                return
            }

            print("FinixSDK: initialized successfully. SDK is ready for use.")
		// listen for delegate to get `deviceDidConnect(_:model:serialNumber:)` before card processing
        }
    }
}

The delegate gets updated with the card terminal's status (e.g., connection, firmware updates, etc.), while the interactionDelegate gets updated with user prompts for the cardholder during the transactions.

While some SDK calls do not require the payment terminal to be connected, most calls need the terminal connected to make a successful request. Confirm these delegates are set and enabled to ensure no issues come up.

De-initialization

Similar to the syncSDK() call to initialize, use unsyncSDK() to disable the connection.

Step 3: Accept In-Person Payments

Now that the payment terminal is connected to the point-of-sale iOS application, your merchant is ready to accept in-person payments.

The iOS Device SDK supports the following in-person use-cases:

Use-case	Description
Create an `Authorization` (capture later)	Authorize funds on the payment card (swiped/dipped/tapped on the payment terminal) and capture the amount later. The capture can be performed either within the SDK or from your backend servers by calling the Finix API.
Create a Sale	Create a sale (also called a `Transfer`) to process a transaction on a card immediately.
Process a Refund	Process a credit to a payment card (swiped/dipped/tapped on the payment terminal).

High-level Overview

With the payment terminal set up, accepting payments with Finix will involve:

The cashier rings up the total amount of the purchase.
Point of Sale iOS application initiates the payment request to the iOS Device SDK.
The iOS Device SDK initiates the sale with the connected payment terminal.
The cardholder enters, swipes, or taps their card.
The payment terminal returns encrypted card data to the Finix SDK.
The iOS Device SDK completes the payment through the Finix API.
The iOS Device SDK returns the transaction status and the required receipt tags to the point of sale application.
The POS application records the payment details and the receipt data to the platform backend.
The POS application provides a receipt to the buyer.

SDK Operations

All the SDK methods provide a completion handler for successes or failures. The handler returns either a success response or an error that contains details of the cause and, if available, the error response.

Here's an example of a signature for a card Authorization:

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func cardAuthorization(_ auth: TransferRequest, completion: @escaping AuthorizationHandler)

The completion handler gets defined as:

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typealias AuthorizationHandler = (_ response: AuthorizationResponse?, _ error: Error?) -> Void

Once the Authorization is complete:

A response gets returned if the request is successful.
A nil response is returned if the request fails, with the error.

Errors

If there is an error TransferError(status:response:) gets returned with:

Field	Description
status	The detailed error reason. Values include: unknown callIssuer declined needsToBeReversed
response	The `TransferResponse`. `AuthorizationResponse` for card authorizations. `SaleResponse` for card sales, etc.

Create an Authorization

An Authorization (also known as a card hold) reserves a specific amount on a card to be captured (i.e., debited) at a later date (usually by the end of the day for card-present authorizations).

We recommend capturing all authorizations using this method to minimize unintended or duplicate payments. You can set your backend system to capture all authorizations at the end of each day if needed. The maximum period for capturing authorizations for in-person payments is two days.

When an authorization is created it produces an Authorization resource:

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let authAmount = Currency(amount: 100, code: .USD)
let authTags: ResourceTags = [:]

let authRequest = TransferRequest(amount: authAmount, tags: authTags)

FinixClient.shared.cardAuthorization(authRequest) { auth, error in
    if let error = error {
        // handle error
        print("Error with Authorization: \(error)")
        return
    }
    if let auth = auth {
        // success
        print("Authorization succeeded: \(auth.amount)")
        print("auth id: \(auth.id)")
    }
}

If any issues come up, similar to other Authorizations in Finix, you can Void an Authorization before it's been captured to cancel the transaction.

Create a Sale

A sale (also called a Transfer) will process a transaction on a card immediately. Transfers take the same request parameters as an Authorization.

A sale can get processed with the following:

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let saleAmount = Currency(amount: 100, code: .USD)
let saleTags: ResourceTags = [:]

let saleRequest = TransferRequest(amount: saleAmount, tags: saleTags)

FinixClient.shared.cardSale(saleRequest) { sale, error in
    if let error = error {
        // handle error
        print("Error with sale: \(error)")
        return
    }
    if let sale = sale {
        // success
        print("Sale succeeded: \(sale.amount)")
        print("transfer id: \(sale.id)")
    }
}

Process a Refund

To return funds to a customer after a Transfer has been approved (or after you have already captured an Authorization), you can use a referenced refund or an unreferenced refund:

Referenced refunds can be submitted from your backend systems and does not require the SDK to interact with the payment terminal.
Unreferenced refunds can get used to return any amount to any card presented to the payment terminal. Since unreferenced refunds aren't tied to a previous Transfer, Finix doesn't have a way to block multiple returns (accidental or fraudulent). We recommend reconciling these unreferenced refunds with the original purchase in your system, to block any of these issues.

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let refundTransferId = TransferId("Trace Id of the transfer")

let refundRequest = RefundRequest(transferId: refundTransferId, amount: refundAmount)

FinixClient.shared.refund(refundRequest) { refund, error in
    if let error = error {
        // handle error
        print("Error with sale: \(error)")
        return
    }
    if let refund = refund {
        // success
        print("Refund succeeded: \(refund.amount)")
        print("transfer id: \(refund.id)")
    }
}

Providing Receipts

Card networks require receipts to have certain data elements for the buyer’s convenience.

After creating a transaction, the iOS Device SDK returns all the data elements required by you to either print or email a receipt to the buyer.

To create receipts, SaleReceipt and RefundReceipt provide all the fields needed to generate a receipt from a card response.

SaleReceipt and RefundReceipt both conform to ReceiptProtocol. They are created with the following:

SaleReceipt(sale: SaleResponse)
SaleReceipt(auth: AuthorizationResponse)
RefundReceipt(refund: CardRefundResponse)

Here is an example of the information (not the layout) available in the receipt and where to find the information in the Finix response.

Sample Receipt:

Sample Receipt

Receipt Data:

No.	Name	ReceiptProtocol Field
1	Merchant Name & Address	`merchantName`, `merchantAddress`
2	Date & Time	`date`
3	Application Label	`applicationLabel`
4	Application Identifier	`applicationIdentifier`
5	Merchant Id	`merchantId`
6	Reference Number	`referenceNumber`
7	Account Number	`accountNumber`
8	Card brand	`cardBrand`
9	Entry Mode	`entryMode`
10	Transaction Id	`transactionId`
11	Approval Code	`approvalCode`
12	Response Code	`responseCode`
13	Response Message	`responseMessage`
14	Amount	`amount`
15	Cryptogram	`cryptogram`
16	Transaction Type	`transactionType`

Handling Tips

We recommend including all tip amounts in the amount being authorized instead of collecting the tip on the receipt and adding it to the capture amount.

To include tips in the authorized amount, include prompts for the cardholder to add the tip in the initial checkout flow on the point of sale iOS application.

Step 4: Post Payments Experience

The following is available through the Finix API, and we recommend completing these steps (as needed) through your backend system.

Use-case	Description
Capture an `Authorization`	Capture a previous `Authorization` to complete the payment.
Void an `Authorization`	Void an `Authorization` to remove the hold from the cardholder’s card account.
Refund a previous payment	Process a refund (full amount or partial amount) for a previously completed payment through Finix.

SDK Conventions

Parameters

The request parameters are a struct. Every field needed to make the calls are required.

Currency

The Currency object includes an amount denominated in a specific currency. Currently only US Dollars are supported.

Completion

Completion handlers take the form of a response and error pair. They get used throughout the iOS Device SDK. Before proceeding, check if there’s an error to handle, then check for a successful response. The completion handlers get delivered on the main thread.

Transfer Identifier

The transfer identifier is present in responses as ID.

State

All of the responses contain a state which represents the transfer’s state.

Delegates

The FinixClient supports two delegates:

delegate which is a FinixDelegate and is primarily concerned with the payment terminal connection and status.
interactionDelegate, which is a FinixClientDeviceInteractionDelegate, handles the text displayed to the buyer (provided by the iOS Device SDK) when interacting with the payment terminal (e.g. “Insert/Tap/Swipe Card”).

Canceling Payment Terminal Operation

To cancel a payment terminal operation call stopCurrentOperation() to stop the terminal from waiting for a card.

Errors

Errors get returned as Error. Where possible a FinixError is returned.

Testing

Test cards and test payment terminals are needed to perform sandbox testing and certification with Finix. Please reach out to your Finix point of contact to get the required test cards and test terminals.

iOS Device SDK

iOS Device SDK Overview

Step 1: Onboard Merchants

Step 1a: Provision Merchant

URL Parameters

Request Arguments

Get the Provisioning Status

Step 1b: Create Merchant Credentials

HTTP Request

URL Parameters

Step 1c: Create Device

HTTP Request

URL Parameters

Request Arguments

Step 2: Pair Terminals

Install the iOS Device SDK

iOS Compatibility

POS iOS App Requirements

Initializing the SDK

Parameters

Step 3: Accept In-Person Payments

High-level Overview

SDK Operations

Errors

Create an Authorization

Create a Sale

Process a Refund

Providing Receipts

Handling Tips

Step 4: Post Payments Experience

SDK Conventions

Next Steps

Managing Payment Terminals

Testing In-Person Payments